In general, road facilities (traffic lights, road lights, CCTVs, iron props, and so on) using electric power are left alone as they are till troubles are checked even though their electric parts are exposed, or adopt safety devices, such as alarms. However, such methods may cause second troubles due to feature changes or troubles of the safety devices.
In order to solve such problem however just a little it may be, Korean Patent No. 10-0553061 discloses a device for warning electric shock hazard with an auxiliary function of a short-circuit prevention, and a partial water-proof structure has been disclosed. However, such prior arts have several problems in that the secondary trouble of the device causes many expenses and requires a predetermined time period till the problem is solved after a warning is checked, and in that another problem frequently occurs due to an exposure of an electric charging part during the time period to solve the problem.
Furthermore, it is impossible to solve problems caused by other factors (for instance, a damage of a track of an underground power line during excavation of a road, a damage of a track of an aerial power line by wind pressure, and water penetration due to another factor).
Moreover, in order to prevent adhesion of advertising posters on the outer peripheral surface of the prop, there are many methods, such as a simple synthetic resin coating, iron coating, pasting of a stone powder mixture, embossment of the prop, fitting of an embossed protection plate, and so on. However, such methods have a problem in that they need removal and maintenance, and a fatal problem in that the electric charging part having electric power is exposed to the surface of the prop along a track of rainwater since rainwater drops down along the prop to the surface of an insulator attached on the outer peripheral surface of the prop.